The present invention relates to a compact turret type tuner arrangement used in television receivers, and more particularly, to VHF television tuners of the turret type.
Generally, mechanical channel selecting devices for VHF television tuners fall into two groups, namely, the rotary-switching type or the turret types. Turret type tuners include an incrementally rotatable channel selector shaft for selectively connecting certain ones of a plurality of tuned circuit elements to each of a plurality of channel selector positions. For example, one such turret tuner arrangement is disclosed in U.S. Pat. No. 3,210,700, wherein a rotatable turret having a plurality of tuning coil units is rotatably mounted on a chassis base. The selected coil unit is connected through terminal contacts to a stator tuning circuit on the chassis base.
The miniaturization of the structure of this kind of mechanical tuners is very difficult in comparison to the rotary switch tuners. However, since television tuners are made in large numbers, it is desirable to provide a low cost turret tuner with a minimum number of parts which may be assembled in an easy and simple manner, in order to be commercially competitive.
In conventional VHF turret tuners, each of the coil units includes an elongate insulating bar, a coil for an RF input stage, a pair of coils for an intermediate stage between the RF and mixer circuits, and a coil for the local oscillator stage. A screw is provided for fine tuning the local oscillator. These coils or windings are wound around the insulating bar, as disclosed, for example, in U.S. Pat. Nos. 3,227,981; 3,337,949; 3,521,677; and 3,594,670. In general, one of the terminal contacts of the coil winding for the oscillator is arranged on a protruding portion at the end of the insulating bar. Therefore, the dimension of turret tuners depends on the length of the protruding portion of said bar.
The conventional detent mechanism, as a means for mounting the rotatable turret on the chassis base, includes a detent wheel fixed on the selector shaft and a spring member mounted on the chassis base, as disclosed in U.S. Pat. Nos. 3,172,062 and 3,234,801. It is also known that this kind of spring member may provide resiliency in two different directions. In another type of turret tuner, a sub-assembly for the stationary circuits comprises a printed circuit board, a stator block having a plurality of strips of spring contacts, and necessary electrical elements soldered to each other, as disclosed in U.S. Pat. No. 3,365,621. Further some devices including lever members, are known as pre-setting, fine tuning devices for VHF turret tuners as disclosed in U.S. Pat. Nos. 3,316,770 and 3,183,726.
Conventional turret tuners still leave room for improvement, especially as far as minimizing the tuner size and dimension, and simplifying the assembly, as well as lowering the manufacture costs and improving the tuner performance are concerned.